Axle assembly with sensor mount

ABSTRACT

A vehicle axle assembly having an axle housing, an axle shaft and a sensor. The axle housing has a tubular portion. A flat is formed on an annular wall of the tubular portion proximate a distal end of the tubular portion. A hole, which intersects the flat, is formed through the tubular portion. The axle shaft can have an integrally formed target portion that includes a plurality of teeth. The sensor is mounted in the hole and abuts the flat to space a tip of the sensor apart from the teeth of the target portion by a predetermined distance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application No.11/001,496 filed on Dec. 4, 2004 which claims the benefit of U.S.Provisional Patent Application Ser. No. 60/555,192 filed on Mar. 22,2004 . The disclosure of the above application is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention generally relates to vehicle axles and moreparticularly to an axle assembly that may include an axle housing withan integral mount for a wheel speed sensor and an axle shaft with anintegral sensor target or exciter ring.

BACKGROUND OF THE INVENTION

Modern vehicles typically include an axle assembly having a housing anda differential assembly. The housing includes a cavity into which thedifferential assembly is positioned. The differential assembly isrotatably supported by the housing within the cavity. The differentialassembly is mechanically coupled to the vehicle engine by a drive shaft.The differential assembly is also coupled to the vehicle drive wheelsvia a pair of axle shafts. The differential assembly regulates drivetorque between the axle shafts, thereby permitting the shafts to rotateat different velocities as when one of the drive wheels is slipping.

Modern automotive vehicles frequently include systems, such as tractionand stability control systems, that identify wheel slip conditions andresponsively control the vehicle (e.g., engine, transmission, brakingsystem) to reduce or eliminate wheel slip in certain instances. In suchsystems, a sensor is typically employed to sense the speed of a wheel oranother component, such as the axle shaft, that has the rotational speedof the wheel.

One relatively common arrangement utilizes a Hall-effect sensor, whichis mounted to the axle housing, and an exciter ring that is typicallypress-fit to the axle shaft. This arrangement typically employs arelatively large boss that is welded to the housing of the axle. Oncethe boss has been secured to the axle housing, several machining stepsare required to drill and ream holes for the sensor, as well as to drilland tap a hole for the fastener that is employed to both orient thesensor and secure the sensor to the axle housing.

While such arrangements are suited for their intended purpose, they arenonetheless susceptible to improvement. For example, an arrangement thatdid not employ a discrete boss would be advantageous in that it wouldeliminate a part, eliminate the welding operation and would permit thesensor to be mounted relatively further outboard toward the brake mountflange where it would permit the sensor to mounted relatively closer toan outboard axle shaft support bearing. This latter aspect is importantin that the sensor could be located to an area where the axle shaftexperienced relatively less deflection. Also, an arrangement that didnot employ a discrete sensor target, such as a sensor ring, would beadvantageous in that it would eliminate a part.

Accordingly, a need exists for an axle assembly with a sensor mountwhich is smaller in size and reduces assembly time.

SUMMARY OF THE INVENTION

In one form, the present teachings provide a vehicle axle assemblyhaving an axle housing, an axle shaft and a sensor. The axle housing hasa tubular portion. A recess or flat is formed on an annular wall of thetubular portion proximate a distal end of the tubular portion, and ahole, which intersects the flat, is formed through the tubular portion.The axle shaft has an integrally formed target portion that includes aplurality of teeth. The sensor is mounted in the hole and abuts the flatto space a tip of the sensor apart from the teeth of the target portionby a predetermined distance.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of an exemplary vehicle constructedin accordance with the teachings of the present invention;

FIG. 2 is a partially cut away perspective view of a portion of thevehicle of FIG. 1 illustrating the rear axle assembly and propshaft ingreater detail;

FIG. 3 is a sectional view of a portion of the rear axle assembly;

FIG. 4 is an exploded perspective view in partial section of the rearaxle assembly; and

FIG. 5 is a sectional view illustrating a portion of a second rear axleassembly constructed in accordance with the teachings of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

With reference to FIG. 1 of the drawings, a vehicle having an axleassembly that is constructed in accordance with the teachings of thepresent invention is generally indicated by reference numeral 10. Thevehicle 10 includes a driveline 12 drivable via a connection to a powertrain 14. The power train 14 includes an engine 16 and a transmission18. The driveline 12 includes a propshaft assembly 20, a rear axleassembly 22 and a plurality of wheels 24. The engine 16 is mounted in anin-line or longitudinal orientation along the axis of the vehicle 10 andits output is selectively coupled via a conventional clutch to the inputof the transmission 18 to transmit rotary power (i.e., drive torque)therebetween. The input of the transmission 18 is commonly aligned withthe output of the engine 16 for rotation about a rotary axis. Thetransmission 18 also includes an output 18 a and a gear reduction unit(not shown). The gear reduction unit is operable for coupling thetransmission input to the output 18 a of the transmission at apredetermined gear speed ratio. The propshaft assembly 20 is coupled forrotation with the output 18 a of the transmission 18. Drive torque istransmitted through the propshaft assembly 20 to the rear axle assembly22 where it is selectively apportioned in a predetermined manner to theleft and right rear wheels 24 a and 24 b, respectively.

With additional reference to FIG. 2, the rear axle assembly 22 is shownto include a differential assembly 26, a left axle shaft assembly 28 anda right axle shaft assembly 30. The differential assembly 26 includes ahousing 32, a differential unit 34 and an input shaft assembly 36. Thehousing 32 supports the differential unit 34 for rotation about a firstaxis 38 and further supports the input shaft assembly 36 for rotationabout a second axis 40 that is perpendicular to the first axis 38.

The housing 32 includes a wall member 42 that defines a central cavity44 having a left axle aperture 46, a right axle aperture 48 and an inputshaft aperture 68. The housing 32 may include a pair of axle tubes 52that are fixedly mounted to the wall member 42. With additionalreference to FIG. 3, the axle tube 52 may include an annular collar 54,which may be formed by swaging or rolling, so as to provide a portion ofthe axle tube 52 with a wall thickness that is relatively thicker thanadjacent portions of the axle tube 52. A recess or flat 56 may be formed(e.g., cast, machined) into the annular collar 54 of the axle tube 52.The flat 56 may be offset from the first axis 38 by a predetermineddistance and may form a datum that will be discussed in greater detail,below. A hole 58, which intersects the flat 56, may be formed throughthe annular collar 54.

The differential unit 34 is disposed within the central cavity 44 of thehousing 32 and includes a gearset 60. The gearset 60 includes first andsecond side gears 62 and 64, respectively, and a plurality of pinions(not shown). The left and right axle shaft assemblies 28 and 30 extendthrough the left and right axle apertures 46 and 48, respectively, wherethey are coupled for rotation about the first axis 38 with the first andsecond side gears 62 and 64, respectively. A flange 66, which may beemployed to support a brake assembly (not shown), may be coupled to adistal end of both the left and right axle shaft assemblies 28 and 30.

The input shaft assembly 36 extends through the input shaft aperture 68where it is supported in the housing 32 for rotation about the secondaxis 40. The input shaft assembly 36 is coupled for rotation with thepropshaft assembly 20 and is operable for transmitting drive torque tothe differential unit 34. More specifically, the drive torque receivedby the input shaft assembly 36 is transmitted to the differential unit34 such that drive torque is distributed to the first and second sidegears 62 and 64, causing the left and right axle shaft assemblies 28 and30 to rotate about the first axis 38.

The left and right axle shaft assemblies 28 and 30 may include an axleshaft 70 that is supported for rotation in the axle tube 52 about thefirst axis 38. Each of the axleshafts 70 may include an externallysplined portion 72 that may meshingly engage a mating internally splinedportion (not specifically shown) that is formed into the first andsecond side gears 62 and 64, respectively.

With reference to FIG. 3, the left axle shaft assembly 28 is shown ingreater detail. As one of ordinary skill in the art would appreciatefrom this disclosure, the left side of the axle assembly is generally amirror image of the right side. As such, a detailed discussion of theleft side will suffice for both. The left axle shaft assembly 28 mayfurther include a bearing 74, axle shaft 70 and a sensor 76 that iscoupled to the axle tube 52. Those of ordinary skill in the art willappreciate from this disclosure that although the particular axleassembly illustrated has a semi-floating configuration, the teachings ofthe present invention are applicable to other types of axle assemblies,including full-floating axle assemblies.

The axle shaft 70 may be integrally formed and may include a bearingsupport portion 78, a target portion 80, and an intermediate portion 82onto which the externally splined portion 72 (FIG. 2) may be formed. Thetarget portion 80 may have a plurality of target features, such asradially-extending, circumferentially spaced-apart teeth 84 that may beformed in a roll forming operation. In the particular example provided,the bearing support portion 78 is formed with a first diameter, theintermediate portion 82 is formed with a second, relatively smallerdiameter and the target portion 80 is formed with a third diameter thatis intermediate the diameters of the bearing support portion 78 and theintermediate portion 82. Appropriately sized and contoured transitionsections 86 may be employed between the bearing support portion 78, thetarget portion 80 and the intermediate portion 82 so as to reduce stressconcentrations, etc.

The bearing 74 may support the axle shaft 70 for rotation in the axletube 52. In this regard, the bearing 74 may be pressed into the axletube 52 such that elements (e.g., rollers 88) support the bearingsupport portion 78 of the axle shaft 70 when the axle shaft 70 isinstalled thereto. A conventional seal 90 may be coupled to the axletube 52 in a conventional manner to retain lubricating fluids in theaxle tube 52 as well as to inhibit the transmission of dirt, debris andother contaminants to the interior of the axle tube 52. The seal 90 mayinclude one or more seal lips 92 that sealingly engage the bearingsupport portion 78 of the axle shaft 70.

If employed, the progressively increasing sizes of the intermediateportion 82, the target portion 80 and the bearing support portion 78permit the axle shaft 70 to be installed to the axle tube 52 withrelatively less risk of damaging the seal 90 as compared with the knownaxle assembly arrangements. In this regard, the target portion 80 of theaxle shaft 70 is relatively smaller in diameter than the bearing supportportion 78 and moreover, the amount by which the axle shaft 70 may betilted relative to the first axis 38 is limited as a result of thelength of the intermediate portion 82.

When the axle shaft 70 is installed to the axle tube 52, the targetportion 80 is radially aligned to the flat 56 that is formed on anannular collar 54 of the axle tube 52. A sensor 76, which may be aHall-effect sensor, may be installed directly to the axle tube 52. Inthe particular example provided, the sensor 76 includes a body portion94 and an abutting flange 96 and the sensor 76 is an active Hall-effectsensor.

The hole 58 in the axle tube 52 may including a mating threaded portion98 that is configured to threadably receive the threads 100 that areformed on the body portion 94 of the sensor 76. The increased thicknessof the annular collar 54 ensures that the threads 100 of the bodyportion 94 and the mating threaded portion 98 engage one another over adistance that is sufficient to fixedly but removably secure the sensor76 to the axle tube 52. Optionally, a sealant (not shown) may be appliedto the threads 100 and/or a seal member, such as an O-ring (not shown),may be employed to form a seal against the axle tube 52 to inhibit fluidcommunication through the hole 58.

In contrast to the known arrangements, the present configurationeliminates two components, i.e., a boss (not shown) that would otherwisebe welded to the axle tube and a discrete sensor target (not shown) thatwould otherwise be coupled, e.g., press-fit, to the axle shaft. Thereduction in part count not only reduces the overall cost of the system,it also improves the performance and reliability of the system throughthe elimination of stack-up. Moreover, as a relatively large boss (notshown) is not employed, the location of the sensor 76 may be placerelatively closer to the flange 66 that supports the brake assembly (notshown).

While the hole 58 has been described thus far as including a matingthreaded portion 98 that is adapted to threadably engage the sensor 76,those skilled in the art will appreciate that the invention, in itsbroader aspects, may be constructed somewhat differently. For example,another mechanical fastening means may be employed to secure the sensorto the axle tube 52 and/or to orient the sensor in a particularorientation as shown in FIG. 5. In this embodiment, the sensor 76 aincludes a mounting flange 120 that is axially spaced apart from anddisposed about the tip 122 of the sensor 76 a. The hole 58 a in the axletube 52 a is not threaded but rather sized to receive a portion of thesensor 76 a. A seal member, such as an O-ring 124, may be fitted aboutthe body of the sensor 76 a and configured to sealingly engage the sideof the hole 58 a. An auxiliary hole 126 is also formed into or throughthe axle tube 52 a and is sized to threadably engage a fastener 128 thatis employed to both secure the sensor 76 a to the axle tube 52 a andorient the sensor 76 a in a desired manner. The fastener 128 is fittedthrough an associated aperture 130 in the mounting flange 120 andthreadably engages the auxiliary hole 126.

While the invention has been described in the specification andillustrated in the drawings with reference to various embodiments, itwill be understood by those skilled in the art that various changes maybe made and equivalents may be substituted for elements thereof withoutdeparting from the scope of the invention as defined in the claims.Furthermore, the mixing and matching of features, elements and/orfunctions between various embodiments is expressly contemplated hereinso that one of ordinary skill in the art would appreciate from thisdisclosure that features, elements and/or functions of one embodimentmay be incorporated into another embodiment as appropriate, unlessdescribed otherwise, above. Moreover, many modifications may be made toadapt a particular situation or material to the teachings of theinvention without departing from the essential scope thereof. Therefore,it is intended that the invention not be limited to the particularembodiment illustrated by the drawings and described in thespecification as the best mode presently contemplated for carrying outthis invention, but that the invention will include any embodimentsfalling within the foregoing description and the appended claims.

1. An axle assembly, comprising: an axle housing defining a centralcavity and including a tubular portion with a sensor mount formedproximate to its distal end, said sensor mount including a recess formedin an outer surface of said tubular portion to define a mount surfaceand a hole extending through said mount surface; a differentialrotatably supported by said axle housing within said central cavity; anaxle shaft rotatably supported in said tubular portion of said axlehousing and having an end portion and a target portion, said end portioncoupled to said differential and said target portion aligned with saidhole in said sensor mount; and a sensor secured to said sensor mountsuch that a tip portion of said sensor is in proximity to said targetportion of said axle shaft and a body portion of said sensor engagessaid mount surface of said recess.
 2. The axle assembly of claim 1wherein said target portion of said axle shaft includes a plurality ofteeth.
 3. The axle assembly of claim 2 wherein said teeth are formedintegrally on said axle shaft.
 4. The axle assembly of claim 1 whereinsaid tubular portion of said axle housing includes a collar having awall thickness that is larger than a wall thickness at said distal endof said tubular portion, and wherein said recess is formed in saidcollar.
 5. The axle assembly of claim 1 wherein said hole through saidmount surface includes threads, and wherein said sensor includes athreaded portion between said tip portion and said body portion adaptedfor threaded retention in said threads of said hole.
 6. The axleassembly of claim 1 wherein said sensor includes a mounting flangeengaging said mount surface and having a hole alignable with a secondhole formed in said mount surface, and wherein a fastener passes throughsaid hole in said mounting flange and is retained in said second hole insaid mount surface for securing said sensor in said recess of saidtubular portion.
 7. The axle assembly of claim 1 wherein said mountsurface is planar and oriented to be generally parallel to a rotary axisof said axle shaft within said tube portion.
 8. An axle assembly,comprising: an axle housing defining a central cavity and first andsecond axle apertures; a first axle tube having a first end secured tosaid first axle aperture and a sensor mount formed proximate its secondend, said sensor mount including a recess formed in an outer surface ofsaid first axle tube to define a mount surface and a hole extendingthrough said mount surface; a second axle tube having a first endsecured to said second axle aperture; a differential rotatably supportedwithin said central cavity and having first and second outputs; a firstaxleshaft rotatably supported within said first axle tube and having afirst end coupled for rotation with said first output of saiddifferential; a second axleshaft rotatably supported within said secondaxle tube and having a first end coupled for rotation with said secondoutput of said differential; and a sensor secured to said sensor mountsuch that a tip portion is in proximity to a target portion of saidfirst axleshaft located proximate to its second end and a body portionengages said mount surface of said recess.
 9. The axle assembly of claim8 wherein said target portion of said first axleshaft includes aplurality of teeth.
 10. The axle assembly of claim 9 wherein said teethare formed integrally on said first axleshaft.
 11. The axle assembly ofclaim 8 wherein said first axle tube includes a collar portion proximateits second end having a wall thickness that is greater than a wallthickness of said second end, and wherein said recess is formed in saidcollar portion.
 12. The axle assembly of claim 8 wherein said holethrough said mount surface includes threads, and wherein said sensorincludes a threaded portion between said tip portion and said bodyportion adapted for threaded retention in said threads of said hole. 13.The axle assembly of claim 8 wherein said sensor includes a mountingflange engaging said mount surface and having a hole alignable with asecond hole formed in said mount surface, and wherein a fastener passesthrough said hole in said mounting flange and is retained in said secondhole in said mount surface for securing said sensor in said recess ofsaid first axle tube.
 14. The axle assembly of claim 8 wherein saidmount surface is planar and oriented to be generally parallel to arotary axis of said first axleshaft within said first axel tube.
 15. Amethod comprising: providing an axle housing having a center chambercommunicating with an elongated axle tube; forming a recess in an outersurface of said axle tube proximate its distal end and a sensor apertureextending through said recess; installing a differential for rotationwithin said center chamber of said axle housing; providing an axleshafthaving a target portion; inserting said axleshaft into said axle tubesuch that its first end is coupled to said differential and its secondend extends outwardly from said axle tube with said target portionaligned with said sensor aperture; and inserting a sensor into saidsensor aperture for aligning its tip portion in proximity to said targetportion and abutting its body portion against said recess.
 16. Themethod of claim 15 further comprising the step of threading said sensorinto said sensor aperture.